The present invention relates to an automatic film loading camera, and more particularly to a film initial-advance apparatus for advancing a film leader portion extending from a film cassette toward a film take-up chamber until the film leader portion is captured by a take-up spool within the film take-up chamber.
Compact cameras of the drop-in loading type having a simple film loading function are now on the market. When the back door of a camera of this type is opened, a cassette inlet is exposed at the bottom of the camera body. A slit is also opened, between the camera body and the back door, into which a film leader portion extending from the film cassette is inserted. As a film cassette is inserted in the axial direction via the cassette inlet into the camera body, the film leader portion is slid via the slit into the camera body and positioned in the film passageway. With such a camera, it is not necessary manually to advance the end of the film leader portion within the film take-up chamber, but it is necessary to conduct an initial advance of the film whereby the film leader portion is reliably captured by the film take-up spool within the film take-up chamber.
A conventional film initial-advance apparatus, as disclosed for example in Japanese Utility Model Laid-open Publ. No. 61-61532, has a film threading member disposed adjacent an exposure frame. A claw or tooth formed on the outer periphery of the film threading member projects into the film passageway. This film threading member is powered by a drive via a one-way clutch and a gear train, the drive also rotating the film take-up spool within the film take-up chamber. When a film cassette is loaded into the film supply chamber and the back door is closed, then the film initial-advance apparatus starts operating. As the claw of the film threading member engages with a perforation in the film leader portion, the film leader portion advances toward the film take-up chamber. When the film leader portion reaches the film take-up spool, perforations of the film leader portion are captured by a plurality of capture members formed on the outer periphery of the film take-up spool. After the film leader portion is completely captured around the film take-up spool by the film initial advance, the film is transported by the film take-up spool because the speed of film advance due to the film take-up spool is higher than that due to the film threading member.
When the film is advanced by the driving force of the spool, the film threading member can be driven in rotation by the film thanks to the one-way clutch so as not to hinder the film advance.
It is also known in the art to provide that a claw of the film threading member is retracted from the film passageway after the film initial advance, so as not to hinder film rewinding.
In recent compact cameras, there has been a tendency to provide a sophisticated function by using as a taking lens a dual-focal-length changeable lens or a zoom lens. Such a taking lens has many lens elements and is large in size. In order to make the size of a camera small when it is not used, it is preferable to retract the taking lens within the camera body to the extent that the rear end of the taking lens is adjacent the exposure frame. However, the film initial-advance apparatus is mounted near the exposure frame so that the taking lens should be in a position spaced from the film initial-advance apparatus. One of the improvements in making a camera compact is therefore to reserve a space for the taking lens near the exposure frame near which the film initial-advance apparatus is mounted.
Referring again to the initial film advance operation, the film leader portion is intermittently advanced as the claw of the film threading member repeatedly engages with and disengages from successive perforations. Accordingly, if the radius of rotary motion of the claw is small, it becomes difficult for the claw to disengage from a perforation. If disengagement does not occur, the claw continues to wind the film so that proper film advance becomes impossible. In view of this, a conventional film threading member has a large diameter. Accordingly, if the film threading member can be made compact while at the same time eliminating the problem of claw disengagement, there would be a great advantage from the viewpoint of saving space for the taking lens near the exposure frame.
Furthermore, a conventional film initial-advance apparatus requires a gear train for the transmission of torque to the one-way clutch and film threading member, which has a tendency to increase the number of components and complicate the structure.